The presidential campaign is entering its final weeks, and unless the polls are completely off, Donald Trump has very little chance of winning — only 7 percent, according to the Times’s Upshot model. Meanwhile, the candidate continues to say disgusting things, and analysts are asking whether down-ballot Republicans will finally repudiate their party’s nominee.

The answer should be, who cares? Everyone who endorsed Mr. Trump in the past owns him now; it’s far too late to get a refund. And voters should realize that voting for any Trump endorser is, in effect, a vote for Trumpism, whatever happens at the top of the ticket.

First of all, nobody who was paying attention can honestly claim to have learned anything new about Mr. Trump in the last few weeks. It was obvious from the beginning that he was a “con artist” — so declared Marco Rubio, who has nonetheless endorsed his candidacy. His racism and sexism were apparent from the beginning of his campaign; his vindictiveness and lack of self-discipline were on full display in his tirades against Judge Gonzalo Curiel and Khizr Khan.

So any politicians who try after the election to distance themselves from the Trump phenomenon — or even unendorse in these remaining few days — have already failed the character test. They knew who he was all along, they knew that this was a man who should never, ever hold any kind of responsible position, let alone become president. Yet they refused to speak out against his candidacy as long as he had a chance of winning — that is, they supported him when it mattered, and only distanced themselves when it didn’t. That’s a huge moral failure, and deserves to be remembered as such.

Of course, we know why the great majority of Republican politicians supported Mr. Trump despite his evident awfulness: They feared retribution from the party’s base if they didn’t. But that’s not an excuse. On the contrary, it’s reason to trust these people even less. We already know that they lack any moral backbone, that they will do whatever it takes to guarantee their own political survival.

And what this means in practice is that they will remain Trumpists after the election, even if the Orange One himself vanishes from the scene.

After all, what we learned during the Republican primary was that the party’s base doesn’t care at all about what the party establishment says: Jeb Bush (remember him?), the initial insider choice, got nowhere despite a giant war chest, and Mr. Rubio, who succeeded him as the establishment favorite, did hardly better. Nor does the base care at all about supposed conservative principles like small government.

What Republican voters wanted, instead, were candidates who channeled their anger and fear, who demonized nonwhites and played into dark conspiracy theories. (Even establishment candidates did that — never forget that Mr. Rubio accused President Obama of deliberately hurting America.)

Just in case you had any doubts about that political reality, a Bloomberg poll recently asked Republicans whose view better matched their own view of what the party should stand for: Paul Ryan or Donald Trump. The answer was Mr. Trump, by a wide margin.

This lesson hasn’t been lost on Republican politicians. Even if Mr. Trump loses bigly, they’ll know that their personal fortunes will depend on maintaining an essentially Trumpist line. Otherwise they will face serious primary challenges and/or be at risk of losing future elections when base voters stay home.

So you can ignore all the efforts to portray Mr. Trump as a deviation from the G.O.P.’s true path: Trumpism is what the party is all about. Maybe they’ll find future standard-bearers with better impulse control and fewer personal skeletons in their closets, but the underlying nastiness is now part of Republican DNA.

And the immediate consequences will be very ugly. Assuming that Hillary Clinton wins, she will face an opposing party that demonizes her and denies her legitimacy no matter how large her margin of victory. It may be hard to think of any way Republicans could be even more obstructionist and destructive than they were during the Obama years, but they’ll find a way, believe me.

In fact, it’s likely to be so bad that America’s governability may hang in the balance. A Democratic recapture of the Senate would be a very big deal, but they are unlikely to take the House, thanks to the clustering of their voters. So how will basic business like budgeting get done? Some observers are already speculating about a regime in which the House is effectively run by Democrats in cooperation with a small rump of rational Republicans. Let’s hope so — but it’s no way to manage a great nation.

Still, it’s hard to see an alternative. For the modern G.O.P. is Mr. Trump’s party, with or without the man himself.